The present invention relates to an automated can decorating apparatus and more particularly to an automated can decorating apparatus that includes a skip-printing mechanism that selectively inhibits or disables the printing of decoration when necessary.
Automated can decorating apparatus having skip-printing mechanisms are well known. The can decorating apparatus includes a mandrel wheel having a plurality of equal-angularly spaced mandrels disposed around its periphery. Each mandrel receives a blank can which is to have decorative features printed on it when the can comes into contact with a printing portion of a blanket wheel as the mandrel wheel is rotated about its axis of rotation. Occasionally, during the automated can decorating process, no blank can is placed on a mandrel or is misplaced on the mandrel. It is desirable to prevent the misplaced can or the empty mandrel from making contact with the blanket wheel to avoid production of a misprinted can, which must be discarded, and/or damage to the empty mandrel.
To overcome this problem many skip-printing mechanism have been proposed. For example, U.S. Pat. No. 3,851,579 to Zurich discloses an automated can decorating apparatus having a skip-print mechanism which moves an individual mandrel away from a printing position to prevent contact with the printing portion of the blanket wheel, when it is detected that the mandrel does not have a can placed on it or has a can misplaced on it, and which then returns the mandrel to a position where it may cause a blank can that is disposed on the mandrel to make contact with the blanket wheel.
U.S. Pat. No. 4,140,053 to Skrypek et al. discloses a skip-printing mechanism which includes an eccentric sleeve having a bore that receives an end of an eccentric shaft and a mandrel that is mounted on the other end of the eccentric shaft. An eccentric sleeve is connected to a power cylinder through a crank arm that extends radially from the eccentric sleeve. Actuation of the power cylinder twists the eccentric shaft which moves the mandrel toward and away from the blanket wheel.
U.S. Pat. No. 4,750,420 to Shriver and U.S. Pat. No. 4,037,530 to Sirvet both disclose skip-printing mechanisms in which the mandrel is mounted on a mandrel holder that is pivoted about a pivoting pin. The axes of the mandrel and the pivoting pin in these mechanisms are parallel but do not coincide. Therefore, the pivoting of the pivoting pin selectively places the mandrel in or out of a contact position. The mandrel holder is pivoted by an arm that is attached to the pivoting pin. The arm is urged at one end thereof to cause the pivoting motion of the mandrel.
U.S. Pat. No. 3,665,853 to Hartmeister, et al. and U.S. Pat. No. 5,148,742 to Stirbis, et al. both disclose skip-print mechanisms in which the printing portion of a blanket wheel can be moved into and out of a contact position with a can on a mandrel. Skip-printing is effected by keeping the printing portion away from a mandrel when it is detected that there is no can on the mandrel or that the can is improperly positioned on the mandrel.
U.S. Pat. No. 4,498,387 to Stirbis, U.S. Pat. No. 4,693,178 to Hudec and U.S. Pat. No. 4,773,326 to Hudec disclose skip-printing mechanisms in which a cam follower on a mandrel holder follows a track. When a can is properly placed on the mandrel, the mandrel holder is directed along a track along which the can makes contact with the printing portion of the blanket wheel. If a can is improperly placed on the mandrel or no can is present, the mandrel holder is directed along a path which will prevent the mandrel contacting the printing portion of the blanket wheel.
U.S. Pat. No. 3,822,639 to Szpitalak and U.S. Pat. No. 3,889,630 to Szpitalak both disclose systems which include a conveyor chain with special links on which mandrels are mounted. A cam can engage a special link to cause the radial movement of the mandrel away from the blanket wheel to effect skip-printing, i.e. to inhibit or disable printing.
U.S. Pat. No. 3,563,170 to Cvacho discloses a skip-printing mechanism in which a mandrel is directed along a path that prevents contact between the mandrel and the printing portion of the blanket wheel when a cam follower, which is attached to the mandrel, engages a camming surface on a cam. The cam is pivotally mounted by a pivot pin, and is pivoted in position to make contact with the cam follower by an actuator.
U.S. Pat. No. 3,279,360 to Smith et al. discloses a can printing machine in which a cam roller urges a mandrel, on which a blank can is placed, against the printing portion of a blanket wheel. The cam roller is itself urged by its engagement with the surface of a cam. To effect skip-printing, the cam is prevented from making contact with the cam roller. As a result, the mandrel is not moved to a position where it may cause a can that is placed on the mandrel to make contact with printing portion of the blanket wheel.
U.S. Pat. No. 3,996,851 to Urban discloses a can printing machine in which a mandrel cam follower engages a mandrel cam to move the mandrel radially toward the printing portion of a blanket wheel to effect printing. To prevent printing, a locking mechanism prevents the cam follower from engaging the cam and thus prevents the mandrel from being radially moved toward the blanket wheel.
U.S. Pat. No. 3,613,571 to Russel et al. shows a mandrel which is mounted at the end of an arm. To effect skip-printing, the arm is pivoted about a point at its end opposite the end on which the mandrel is mounted, in order to move the mandrel away from the blanket wheel.
It is an object of the present invention to provide an automated can decorating apparatus that includes a skip-printing mechanism for inhibiting or disabling printing by the can decorating apparatus.
According to the present invention, mandrel subassemblies having a mechanical mandrel trip are incorporated in an automated can decorating apparatus, which includes a mandrel wheel and a blanket wheel. Each mandrel subassembly is mounted to the periphery of the mandrel wheel. Each mandrel on the mandrel wheel receives a blank can in a conventional manner. To print on the can, the can on the mandrel is pressed against the printing portion of the blanket wheel as the mandrel wheel and blanket wheel rotate in a conventional manner. When it becomes necessary to disable the printing operation, e.g. when a can is missing or not properly positioned on a mandrel, the mechanical mandrel trip moves that mandrel to prevent the can improperly positioned or the uncovered mandrel making contact with the printing portion of the blanket wheel.
An embodiment of the present invention includes a plurality of support arms mounted around the outer circumference of a mandrel wheel. Each support arm has a mandrel shaft support which is in the form of a transverse bore in which a first non-eccentric portion of an eccentric mandrel shaft is rotatably received. A second eccentric portion of each eccentric mandrel shaft has a mandrel rotatably received on its outer surface and the second portion thus serves as a mandrel seat. The second portion of each eccentric mandrel shaft has a central axis which is offset from the central axis of the first portion of the eccentric mandrel shaft.
A trip lever member is attached to a stub portion of the first portion of the eccentric mandrel shaft, and the stub shaft extends outwardly from the transverse bore in the arm. Movement of the trip lever member rotates the eccentric mandrel shaft about the central axis of the first portion of the eccentric mandrel shaft, thereby causing the second portion, i.e. the mandrel seat, to rotate eccentrically about the central axis of the first portion. Thus, rotation of the first portion of the eccentric mandrel shaft in one direction moves the uncovered mandrel or the blank can that is not to be printed, which is on the second portion of that shaft, to move along a path having a radial component toward the center of the mandrel wheel, away from the blanket wheel. Rotation of the first portion of the eccentric shaft in the opposite direction moves the mandrel carrying a correctly positioned can along a path having a radial component radially out from the center of the mandrel wheel to a position where the blank can that is on the mandrel can contact the printing portion of the blanket wheel.
The trip lever member includes a trip arm and a reset arm which are angularly spaced from one another around the eccentric shaft and are connected to the first portion of the eccentric shaft by a sleeve member. The trip arm has a trip cam follower disposed on it and the reset arm has a reset cam follower disposed on it. A moveable trip plate is selectively moved to engage a selected one of the trip cam followers. The engagement of a trip cam follower on the trip arm of a trip lever with the trip cam plate rotates the eccentric mandrel shaft to which the trip lever is attached in one direction to move the mandrel that is mounted on the second portion of the eccentric mandrel shaft on a path with a radial component toward the center of the mandrel wheel and away from the blanket wheel.
A reset cam plate is positioned to engage the reset cam follower on a trip lever member that had been moved due to engagement with the trip cam plate. The engagement of a reset cam follower and the reset cam plate causes the trip lever to rotate its associated mandrel away from the center of the mandrel wheel on a path with a radial component and to a position where a blank can on the mandrel may contact the printing portion of the blanket wheel.
An over-center spring holds an associated mandrel against the printing portion in the print position and also urges the mandrel toward a non-print position where the mandrel is spaced away from the printing portion of the blanket wheel.
According to an embodiment of the invention, there are two moveable trip cam plates, each capable of only engaging one respective group of the trip cam followers. Each trip cam plate is moved into a position to contact a trip cam follower by the actuation of a respective air-actuated piston arm.